Diagnostic role of internal mammary lymph node involvement in tuberculous pleurisy: a multicenter study.

BACKGROUND AND OBJECTIVES: Diagnosis of tuberculous pleurisy (TP) may be challenging and it often requires pleural biopsy. A tool able to increase pre-test probability of TP may be helpful to guide diagnostic work-up and enlargement of internal mammary lymph node (IMLN) has been suggested to play a potential role. The aim of the present investigation was to assess role of IMLN involvement in TP in a multi-centric case-control study, by comparing its prevalence and test performance to those observed in patients with infectious, non-tuberculous pleurisy (NTIP), and in controls free from respiratory diseases (CP). METHODS: A total of 419 patients, from 14 Pulmonology Units across Italy were enrolled (127 patients affected by TP, 163 affected by NTIP and 129 CP). Prevalence, accuracy and predictive values of ipsilateral IMLN involvement between cases and control groups were assessed, as well as concordance between chest computed tomography (CT scan) and thoracic ultrasound (TUS) measurements. RESULTS: The prevalence of ipsilateral IMLN involvement in TP was significantly higher than that observed in NTIP and CP groups (respectively 77.2%, 39.3% and 14.7%). Results on test performance, stratified by age, revealed a high positive predictive value in patients aged ≤50 years, while a high negative predictive value in patients aged >50 years. The comparison between CT scan and ultrasound showed moderate agreement (Kappa=0.502). CONCLUSIONS: Evaluation of IMLN involvement plays a relevant role in assessing the pre-test probability of TP. Considering the increasing global prevalence of mycobacterial infections, a tool able to guide diagnostic work-up of suspected TP is crucial, especially where local sources are limited.

Respiratory and peripheral muscular ultrasound characteristics in ICU COVID 19 ARDS patients.

PURPOSE: Severe cases of coronavirus disease 2019 develop ARDS requiring admission to the ICU. This study aimed to investigate the ultrasound characteristics of respiratory and peripheral muscles of patients affected by COVID19 who require mechanical ventilation. MATERIALS AND METHODS: This is a prospective observational study. We performed muscle ultrasound at the admission of ICU in 32 intubated patients with ARDS COVID19. The ultrasound was comprehensive of thickness and echogenicity of both parasternal intercostal and diaphragm muscles, and cross-sectional area and echogenicity of the rectus femoris. RESULTS: Patients who survived showed a significantly lower echogenicity score as compared with those who did not survive for both parasternal intercostal muscles. Similarly, the diaphragmatic echogenicity was significantly different between alive or dead patients. There was a significant correlation between right parasternal intercostal or diaphragm echogenicity and the cumulative fluid balance and urine protein output. Similar results were detected for rectus femoris echogenicity. CONCLUSIONS: The early changes detected by echogenicity ultrasound suggest a potential benefit of proactive early therapies designed to preserve respiratory and peripheral muscle architecture to reduce days on MV, although what constitutes a clinically significant change in muscle echogenicity remains unknown.

Tocilizumab in COVID-19 interstitial pneumonia.

BACKGROUND: Published reports on tocilizumab in COVID-19 pneumonitis show conflicting results due to weak designs or heterogeneity in critical methodological issues. METHODS: This open-label trial, structured according to Simon's optimal design, aims to identify factors predicting which patients could benefit from anti-IL6 strategies and to enhance the design of unequivocal and reliable future randomized trials. A total of 46 patients with COVID-19 pneumonia needing of oxygen therapy to maintain SO2 > 93% and with recent worsening of lung function received a single infusion of tocilizumab. Clinical and biological markers were measured to test their predictive values. Primary end point was early and sustained clinical response. RESULTS: Twenty-one patients fulfilled pre-defined response criteria. Lower levels of IL-6 at 24 h after tocilizumab infusion (P = 0.049) and higher baseline values of PaO2/FiO2 (P = 0.008) predicted a favourable response. CONCLUSIONS: Objective clinical response rate overcame the pre-defined threshold of 30%. Efficacy of tocilizumab to improve respiratory function in patients selected according to our inclusion criteria warrants investigations in randomized trials.

Broadband Epsilon-near-Zero Reflectors Enhance the Quantum Efficiency of Thin Solar Cells at Visible and Infrared Wavelengths.

The engineering of broadband absorbers to harvest white light in thin-film semiconductors is a major challenge in developing renewable materials for energy harvesting. Many solution-processed materials with high manufacturability and low cost, such as semiconductor quantum dots, require the use of film structures with thicknesses on the order of 1 µm to absorb incoming photons completely. The electron transport lengths in these media, however, are 1 order of magnitude smaller than this length, hampering further progress with this platform. Herein, we show that, by engineering suitably disordered nanoplasmonic structures, we have created a new class of dispersionless epsilon-near-zero composite materials that efficiently harness white light. Our nanostructures localize light in the dielectric region outside the epsilon-near-zero material with characteristic lengths of 10-100 nm, resulting in an efficient system for harvesting broadband light when a thin absorptive film is deposited on top of the structure. By using a combination of theory and experiments, we demonstrate that ultrathin layers down to 50 nm of colloidal quantum dots deposited atop the epsilon-near-zero material show an increase in broadband absorption ranging from 200% to 500% compared to a planar structure of the same colloidal quantum-dot-absorber average thickness. When the epsilon-near-zero nanostructures were used in an energy-harvesting module, we observed a spectrally averaged 170% broadband increase in the external quantum efficiency of the device, measured at wavelengths between 400 and 1200 nm. Atomic force microscopy and photoluminescence excitation measurements demonstrate that the properties of these epsilon-near-zero structures apply to general metals and could be used to enhance the near-field absorption of semiconductor structures more widely. We have developed an inexpensive electrochemical deposition process that enables scaled-up production of this nanomaterial for large-scale energy-harvesting applications.

The prevalence and clinical significance of premature ventricular beats in the athlete.

Adolescents and adults with cardiovascular disease who are engaged in sports activity have an increased risk of sudden cardiac death (SCD) that is three times greater than that of their non-athletic counterparts. Sport acts as a trigger for cardiac arrest in the presence of underlying cardiovascular diseases predisposing to life-threatening ventricular arrhythmias. Frequent and complex premature ventricular beats (PVBs) detected during the cardiovascular screening of the athletic population may be a sign of an underlying cardiovascular disease at risk of SCD, but are also often recorded in trained athletes without cardiovascular abnormalities. Thus, the interpretation of PVBs could represent a clinical dilemma, particularly in the athlete. However, while some characteristics of PVBs can be considered common and benign, others occur uncommonly in the athletic population and raise the suspicion of an underlying cardiovascular disease. This review discusses the prevalence and clinical significance of PVBs in the athlete, with a focus on exercise-induced PVBs, on the analysis of PVB's morphology at 12-lead ECG, and on the morphological substrates identified by imaging techniques. The implications on eligibility for competitive sports participation are also discussed, according to the relevance of PVB detection for disqualifying athletes from competitions.

Hypersensitivity Pneumonitis: A Comprehensive Review.

Hypersensitivity pneumonitis (HP), also known as extrinsic allergic alveolitis, is a complex pulmonary syndrome mediated by the immune system and caused by inhalation of a wide variety of antigens to which the individual has been previously sensitized. The pathobiology of the disease is not fully understood, but in addition to the triggers that initiate the disease, host/genetic factors are likely to be important, as only a minority of exposed individuals develop HP. Due to the lack of a diagnostic gold standard, the diagnosis of HP is not straightforward and relies on the integration of a number of factors, including history of exposure, precipitating antibodies to the offending antigen, clinical features, bronchoalveolar lavage, and radiological and pathologic features. However, in the appropriate setting, a high index of suspicion is critically important and may obviate the need for more invasive tests. Clinical presentation and natural history vary widely. Acute forms generally resolve without sequelae, while chronic forms, which are caused by persistent low-grade exposures, are associated with poor prognosis. Corticosteroids may be useful in acute episodes for symptomatic relief or in chronic and progressive disease, but their long-term efficacy has never been validated in prospective clinical trials. Ideally, patients with HP should be referred to centers with expertise, as the overlap with other forms of interstitial lung disease may be substantial. Making the correct diagnosis has critical therapeutic and prognostic implications.

A quantitative assessment of circulating progenitor cells in competitive athletes and in sedentary subjects.

AIM: Hematopoietic stem cells (HSCs) and endothelial progenitor cells (EPCs) are known to play a role in the vascular responses and adaptations to exercise. We performed a quantitative assessment of HSCs and EPCs in adolescents in order to investigate whether resting levels of circulating HSCs and EPCs are comparable between elite athletes and sedentary healthy subjects. METHODS: HSCs and EPCs levels were measured in adolescent competitive football players and in age- and sex-matched sedentary controls. A laboratory testing was also performed to determine the white blood cells count and the lipid profile. All athletes were evaluated at the same stage of their training program, after 6 months of training. Controls were not engaged in any kind of routine training program. RESULTS: Twenty male competitive athletes (18.4 ± 0.5 years) and 9 sedentary controls (18.7 ± 0.4 years) participated in the study. As expected, HDL cholesterol was higher in athletes as compared with controls (P<0.05). No significant differences in the other laboratory parameters were observed among groups. Circulating levels of HSCs were significantly lower in athletes in comparison with sedentary controls (P<0.05). Conversely, EPCs and KDR+ cell subpopulations did not substantially differ between athletes and controls. CONCLUSION: Adolescent athletes exhibit lower levels of circulating HSCs but not of EPCs compared to sedentary controls. The process of tissue repair associated with intensive training can contribute to this difference, acting as a stimulus for mobilization and homing of HSCs in the site of injuries.

Water polo throwing velocity and kinematics: differences between competitive levels in male players.

AIM: In water polo, throwing is one of the most important and frequently used technical skills for the player. There is no scientific literature that provides information about differences in throwing between elite and sub-elite water polo players. The aim of our study was to study differences in throwing velocities and kinematic variables in elite and sub-elite level male water polo players. METHODS: We considered the variables under standardized conditions during a typical motion, the five-meter shot (penalty). Thirty-four athletes from the Men's First Division Water Polo Championship and forty-two players participating in the National Fourth Division League, took part in the study. Video analysis measures were taken with high-speed digital cameras and the videos were analyzed offline with Dartfish 5.0 Pro. RESULTS: No correlation was found between body mass, height and throwing velocity. Elite players had higher values ​for ball speed (22.8±2.4 m/s for elite team and 18.4±1.7 m/s for sub-elite team; P=0.002) and greater elbow angle (157.5±10.3 degree for elite team versus 146.7±8.9 degree for sub-elite team; P=0.002). In elite team the throwing time was lower (165.6±22.2 and 188.6±23.9 ms, respectively; P=0.05) and the shoulder angle was smaller (115.1±10.3 and 123.8±12.4 degree, respectively; P=0.03) than in sub-elite team. Head height was significantly greater in elite players (elite players 71.1±8.7 cm, sub-elite players 65.6±6.2 cm; P=0.03). CONCLUSION: Differences in kinematic characteristics between elite and sub-elite players were showed. Differences in elbow and shoulder action must be considered both in training and injury prevention.

Hypersensitivity pneumonitis: a comprehensive review

Hypersensitivity pneumonitis (HP), also known as extrinsic allergic alveolitis, is a complex pulmonary syndrome mediated by the immune system and caused by inhalation of a wide variety of antigens to which the individual has been previously sensitized. The pathobiology of the disease is not fully understood, but in addition to the triggers that initiate the disease, host/genetic factors are likely to be important, as only a minority of exposed individuals develop HP. Due to the lack of a diagnostic gold standard, the diagnosis of HP is not straightforward and relies on the integration of a number of factors, including history of exposure, precipitating antibodies to the offending antigen, clinical features, bronchoalveolar lavage, and radiological and pathologic features. However, in the appropriate setting, a high index of suspicion is critically important and may obviate the need for more invasive tests. Clinical presentation and natural history vary widely. Acute forms generally resolve without sequelae, while chronic forms, which are caused by persistent low-grade exposures, are associated with poor prognosis. Corticosteroids may be useful in acute episodes for symptomatic relief or in chronic and progressive disease, but their long-term efficacy has never been validated in prospective clinical trials. Ideally, patients with HP should be referred to centers with expertise, as the overlap with other forms of interstitial lung disease may be substantial. Making the correct diagnosis has critical therapeutic and prognostic implications (AU)

La neumonitis por hipersensibilidad (NH), también conocida como alveolitis alérgica extrínseca, es un síndrome pulmonar complejo mediado por el sistema inmune y provocado por la inhalación de una amplia variedad de alérgenos frente a los cuales el paciente está previamente sensibilizado. La patogénesis de la enfermedad se conoce parcialmente; sin embargo, además de los activadores iniciales que dan lugar al desarrollo de la enfermedad hay factores genéticos que tienen importancia también, de tal forma que solo una minoría de los individuos expuestos desarrollan la enfermedad. Debido a la falta de un 'gold estándar' para el diagnóstico de NH, se hace necesaria la integración de un número de factores, entre los que se encuentran la historia de exposición al alérgeno, la presencia de anticuerpos precipitantes frente al Ag ofensor, datos clínicos y datos patológicos en el lavado broncoalveolar, y radiológicos. En cualquier caso un alto índice de sospecha clínica es crítica y puede obviar la necesidad de otros test más invasivos. La presentación clínica y la historia natural de la enfermedad puede variar ampliamente desde las formas agudas que generalmente se resuelven sin secuelas a las formas crónicas fibróticas que son provocadas por la exposición de grado bajo mantenida y que se asocian con un peor pronóstico. Los corticosteroides pueden ser útiles en el tratamiento sintomático de los episodios agudos o en la enfermedad crónica progresiva, pero su eficacia a largo plazo nunca ha sido validada en ensayos clínicos diseñados para ese fin. La dinámica adecuada debe dirigir a los pacientes con MH a centros especializados expertos, dado que puede haber otras formas solapadas de enfermedad pulmonar y el diagnóstico correcto es crítico para la aplicación de un correcto tratamiento y un mejor pronóstico (AU)

The contribution of underwater kicking efficiency in determining "turning performance" in front crawl swimming.

AIM: The aim of this study was to analyze the effects: 1) of maximal velocity (vout max) and acceleration (aout max) attained during the turn; 2) of deceleration (-aglide) and glide efficiency (GE) in the gliding phase after the turn; and 3) of the efficiency (hF) of the dolphin kick in determining the velocity and acceleration in the first 5 and the following 10 m after a turn (v5, v5-15, a5 and a5-15) in a 100 m simulated front crawl race. METHODS: The experiments were conducted on 13 swimmers (7M/5F) and all the above mentioned parameters were derived from underwater kinematical analysis. RESULTS: The 100 m times were smaller the larger v5, v5-15, a5 and a5-15. In turn, v5, v5-15, a5 and a5-15 were significantly related to vout max and aout max as well as to ηF and GE (R>0.57, P<0.05). CONCLUSION: Data reported in this study indicate that in the first 5-15 m after the turn, velocity is essentially sustained by the force generated by the swimmer on the pool wall but also indicate the importance of an efficient dolphin kick (and of a streamlined glide) in determining the values of velocity and acceleration in this phase of the race.

Alcohol drinking and non-Hodgkin lymphoma risk: a systematic review and a meta-analysis.

BACKGROUND: Whether an association between alcohol drinking and non-Hodgkin lymphoma (NHL) risk exists is an open question. In order to provide quantification of the issue, we carried out a meta-analysis of published data. METHODS: We identified 21 case-control and 8 cohort studies, including a total of 18,759 NHL cases. We derived meta-analytic estimates using random-effects models, taking into account correlation between estimates. RESULTS: The overall relative risk (RR) of NHL for drinkers versus non-drinkers was 0.85 [95% confidence interval (CI) 0.79-0.91]. Compared with non-drinkers, the pooled RRs were 0.88 for light (≤1 drink per day), 0.87 for moderate (1 to <4 drinks per day), and 0.84 for heavy (≥4 drinks per day) alcohol drinking. There was no association for light drinkers in cohort studies, whereas for moderate and heavy drinkers, the RRs were similar in case-control (0.85 for moderate, 0.92 for heavy) and cohort (0.89 for moderate, 0.79 for heavy) studies. The inverse relation with alcohol consumption (drinkers versus non-drinkers) was similar in men (RR = 0.83) and women (RR = 0.86), but apparently stronger in studies from Asia (RR = 0.69) than other world areas (RR = 0.88). CONCLUSION: This meta-analysis provides quantitative evidence of a favourable role of alcohol drinking on NHL risk, though the lack of a biological explanation suggests caution in the interpretation of results.

Throwing velocity and kinematics in elite male water polo players.

AIM: Fifty-three members of the Italian Men Water Polo Team were filmed using two synchronized cameras, while they were shooting a goal. Considering the differences in body mass, height, training strategies and the technical-tactical features of the players, the aims of this study were to employ video-analysis techniques in order to investigate selected kinematic parameters in water polo throwing, and to provide comprehensive quantitative information on the throwing movement in relation to the different team player positions. METHODS: Video analysis was used to estimate the elbow angle at release, the shoulder angle at follow through, the back and head height at ball release, trunk rotation angle and ball velocity at release. RESULTS: Ball release velocities ranged from 21.0 to 29.8 m/s (average value 25.3±1.4 m/s), for field players. Goal keepers show the lowest team values (average 21.7±0.3 m/s). Similar to previous study results, ball release was typically reached just prior to the elbow approaching full extension (151.6±3.6°), and the follow through shoulder angle was 143±5.9°. CONCLUSION: No significant statistical difference was recorded between injured and non-injured athletes. No positive association was demonstrated between physical characteristics (body mass and height) and ball velocity.

Physiological profile of water polo players in different competitive levels.

AIM: The purpose of this study was to determine if there are different physiological characteristics in water polo players of three different competitive levels (national team, NT, junior national team, NJ, and amateur club, AC). METHODS: To better define the training levels of water polo players competing at different levels, we administered a shuttle swim test (SST, a specific test used by Italian coaches) and a classic speed-lactate test. The shuttle swim test is based on actions at maximum intensity followed by incomplete recoveries. To compare the athletes, we used their morphological characteristics, the speed during an incremental test associated with fixed blood lactate concentrations of 2 mmol*1-1 (Aerobic Threshold, AT) and 4 mmol*1-1 (Anaerobic Threshold, AnT), and the SST data (speed, heart rate and lactate concentration). RESULTS: The heart rate at the end of the SST was 164+/-12 beats*min-1 for NT, 166+/-10 beats*min-1 for NJ (no significant difference, P>0.05) and 179+/-9 beats*min-1 for AC (significantly different from NT and NJ, P<0.05). The AT and AnT speeds were significantly higher in NT than in AC and NJ (P<0.05). No significant differences were found in AT and AnT speeds between AC and NJ (P>0.05). The mean speed during the shuttle swim test was significantly higher in NT and NJ than in AC (P<0.05). Lactate values were similar in the NT, AC and NJ groups (P>0.05). The SST mean speed was significantly correlated with the AT (P<0.01) and AnT speeds (P<0.05) in three groups . In all groups no significant correlation was found between SST blood lactate and AT or AnT speeds (P>0.05). CONCLUSION: Some differences were found among the senior and junior professional and amateur water polo players in both SST performance and Aerobic and Anaerobic Thre-shold speeds. The shuttle swim test for water polo provides conditioning coaches and sport scientists with data on the sport-specific movement speed and the competition-specific fatigue resistance in each athlete.

Shuttle swim test for water polo players: validity and reliability.

AIM: The purpose of this study, carried out on elite water polo players, was to examine: 1) the relationship between the shuttle swim test (SST) and the performance during official water polo games, and 2) the SST reliability. METHODS: Sixteen male players of the Italian National Water Polo Team (age: 27.9 + or - 2.1 years, body mass: 88.5 + or - 10.3 kg, height: 186.6 + or - 6.9 cm) performed the SST, consisting of two sets of seven repetitions from 40 to 10 m (total of 120 m for each set) at a maximal intensity with 90 s of rest between sets. During the SST, average swimming speed, blood lactate concentration and heart rate were recorded. Direct validity of the SST was evaluated by comparing the average swimming speed with the total distance covered (TD) and the distance covered at high intensity swimming (above 1.8 m x s(-1), HIS) during three official water polo games. SST reliability was assessed by testing the same athletes one week apart. RESULTS: Average swimming speed during the SST was significantly correlated with TD (r=0.67, P<0.01) and HIS (r=0.74, P<0.004). The mean average speed during SST showed high reliability (TE=0.4%; CI 95%: 0.2% to 1.0% ). The T1 vs. T2 difference in mean average speed was not significant. CONCLUSIONS: Present findings demonstrate the validity and reliability of the SST for evaluation of the swimming fitness of water polo players.

Glucocorticoid receptor mRNA expression in peripheral blood mononuclear cells in high trained compared to low trained athletes and untrained subjects.

BACKGROUND: Physiological needs during prolonged exercise are a potent stimulus for the hypothalamic-pituitary-adrenal (HPA) axis. Hence, athletes undergoing daily endurance training sessions may have frequent and prolonged phases of endogenous hypercortisolism. Since chronic glucocorticoids treatment leads to down-regulation of glucocorticoid receptor alpha (GR-alpha) mRNA expression, endurance training could lead to modulation of GR expression. AIM: The aim of the study was to evaluate GR-alpha and GR-beta mRNA expressions in peripheral blood mononuclear cells and plasma cortisol, ACTH and cortisol binding globulin (CBG) concentrations at rest in subjects undergoing different training regimes. SUBJECTS AND METHODS: Nine high trained (HT) swimmers (training volume: 21.6+/-1.7 hours/week in 10-12 sessions) were compared with two age-matched control groups represented by 8 low trained (LT) runners (training volume: 6.4+/-2.6 h/week in 3-5 sessions) and 9 untrained subjects. Expression of GR was determined by RT-PCR of total RNA. Hormone levels were determined by radioimmunoassay methods. RESULTS: HT athletes showed 10 times less GR-alpha mRNA expression than the untrained subjects, while LT athletes exhibited values about twofold less than the untrained subjects. GR-beta mRNA expression was undetectable in all subjects. No differences were observed among the three groups in hormone levels. CONCLUSIONS: GR- alpha mRNA expression is repressed in proportion to the amount and frequency of the stressful stimuli due to training. Hence, this down-regulation may be a consequence of the frequent and prolonged exposure to cortisol acute elevations induced by training. GR-beta did not play an important role in inducing the down-regulation of GR-alpha mRNA expression observed.

One-year efficacy of a 3-week intensive multidisciplinary non-pharmacological treatment program for fibromyalgia patients.

OBJECTIVE: The aim of the present study was to investigate the long-term efficacy of a 3-week intensive residential multidisciplinary non-pharmacological treatment program (including individually prescribed and monitored aerobic exercise and cognitive behavioural therapy) on fibromyalgia symptoms and aerobic fitness. METHODS: Twenty-five women with fibromyalgia participated in six experimental sessions (pre-admission, immediately before and immediately after the treatment, and to 2, 5 and 12 months afterwards) in which they underwent clinical, psychophysical and psychological examinations: pain intensity (VAS), pain area (percentage of total body surface), deep pressure pain threshold at 18 tender point sites measured with a pressure algometer, an incremental step test with blood lactate determination and calculation of the individual intensity of exercise corresponding to 2 mM of lactate concentration (W2, index of aerobic fitness). Depression and coping were evaluated with the Center for Epidemiologic Studies Depression Scale (CES-D) and Brief Pain Coping Inventory (BPCI), respectively. RESULTS: Pain intensity, pain area and number of positive tender points were significantly reduced up to 12 months, while deep pressure pain threshold and W2 increased. CES-D score decreased until two months. Among the 18 items of the BCPI, only item 3 ("physical exercise/stretching") changed significantly, increasing until 12 months. CONCLUSION: In fibromyalgia patients, whose symptoms before treatment were constant, a 3-week intensive residential multidisciplinary treatment program showed one-year efficacy in improving pain and aerobic fitness. The acquisition of physical exercise as a coping strategy for chronic pain acceptance could explain the long-term effects of our brief treatment.

Anticipatory control of impending postural perturbation in elite springboard divers.

Among athletes, elite springboard divers (ED) should develop an optimal anticipatory control of postural stability, as a result of specific training. Postural strategies of ED and healthy subjects (HS) while expecting an impending perturbation were compared. The mean center of pressure (COP) position was analyzed during control quiet stance (cQS) and during anticipatory quiet stance (aQS(1-4)), i.e., in expectation of four backward translations of the support surface. During cQS, COP position in ED was not significantly different as compared to HS. During aQS(1-4,) a significant increase in the mean COP position was observed in both groups with ED adopting a more forward inclined vertical alignment than HS. In ED specific training may have resulted in a reference frame offset in a more anterior direction while expecting an impending perturbation. We suggest that leaning more forward may represent a more reliable way of coping with predictable perturbations of postural stability.

The assessment of path linearity in swimming: a pilot study.

The lateral-medial displacement (LF) and the overall drift from a straight path (DT) were quantified and compared in 5 top-level (TLS) and 5 low-level (LLS) crawl swimmers. Sixteen repetitions of 25-m crawl at increasing intensity were performed and videotaped. The performances were divided into 3 intensities (< 80 %, 80 - 90 % and > 90 % of maximal speed). LF was expressed as overlength swum (OLS) and coefficient of variation (CV) of the Z-component movement. OLS revealed a significant main effect for swimmer level (p < 0.01), intensity (p < 0.01) and their interaction (0.48, 0.37, 0.31-m for TLS and 0.47, 0.43, 0.44-m for LLS, p < 0.05). CV was significantly higher in LLS at the lowest (0.69 vs. 0.22, p < 0.05) and highest intensity (0.71 vs. 0.33, p < 0.05). DT, expressed as the slope of the linear regression of position data vs. time, was significantly higher in LLS only at the highest intensity (0.025 vs. 0.013, p < 0.05). The amount of dissipated energy due to LF, quantified by means of discrete Fourier analysis, revealed a difference only when the 0 - 5 Hz and 5 - 10 Hz spectral windows were analysed separately. While LF has a practical significance since it contributes to increase drag, DT is negligible at least for short-distance events.

Wrist stabilisation and forearm muscle coactivation during freestyle swimming.

The aim of this study was to evaluate the stabilisation of the wrist joint and the ad hoc wrist muscles activations during the two principal phases of the freestyle stroke. Seven male international swimmers performed a maximal semi-tethered power test. A swimming ergometer fixed on the start area of the pool was used to collect maximal power. The electromyography signal (EMG) of the right flexor carpi ulnaris (FCU) and extensor carpi ulnaris (ECU) was recorded with surface electrodes and processed using the integrated EMG (IEMG). Frontal and sagittal video views were digitised frame by frame to determine the wrist angle in the sagittal plane and the principal phases of the stroke (insweep, outsweep). Important stabilisation of the wrist and high antagonist muscle activity were observed during the insweep phase due to the great mechanical constraints. In outsweep, less stabilisation and lower antagonist activities were noted. Factors affecting coactivations in elementary movements, e.g. intensity and instability of the load, accuracy and economy of the movement were confirmed in complex aquatic movement.